Narcosis apparatus

ABSTRACT

STEM EXTENSION IS MADE, AND SAID THROTTLE AND VALVE MEANS HAVING MEANS PROVIDED TO ENGAGE EACH OTHER. AN APPARATUS FOR THE VAPORIZATION OF AN ANESTHETIC HAS BEEN PROVIDED WHICH APPARATUS ACHIEVES IMPROVED CONTROL IN RESPECT TO THE AMOUNT OF ANESTHETIC ADMINISTERED TO A PATIENT. THE APPARATUS COMPRISES A DISTRIBUTION CHAMBER FOR A GAS, A FIRST CONDUIT FROM THE DISTRIBUTION CHAMBER INTO A CHAMBER IN WHICH THE ANESTHETIC IS VAPORIZED, A TEMPERATURE SENSING MEANS IN SAID VAPORIZATION CHAMBER, A SECOND BYPASS CONDUIT FROM THE DISTRIBUTION CHAMBER HAVING A THROTTLE MEANS INTERPOSED THEREIN, SAID SECOND CONDUIT LEADING TO A MIXING CHAMBER, AN OUTLET CONDUIT LEADING FROM THE VAPORIZATION CHAMBER TO THE MIXING CHMABER AND HAVING A VALVE MEANS INTERPOSED THEREIN, SAID THROTTLE MEANS IN SAID BYPASS CONDUIT HAVING AN ANNULAR SLOT DEFINED BY A MOVABLE ELEMENT ON A THROTTLE STEM EXTENSION, SAID STEM EXTENSION PROTRUDING INTO THE VAPORIZATION CHAMBER AND HAVING A SLEEVE SURROUNDING THE SAME, MEANS FOR FASTENING SAID SLEEVE AND SAID STEM EXTENSION, SAID SLEEVE BEING OF A MATERIAL HAVING A HIGHER THERMAL COEFFICIENT OF EXPANSION THAN THE MATERIAL OF WHICH THE

United States Patent [72] Inventor Hans George Breiling Lubeck, Germany 121] App]. No. 768,107

[22] Filed Oct. 16, 1968 [45] Patented June 28, 1971 [73] Assignee Dragerwerlr, Heinr. 8; Bernh. Drager Lubeck, Germany [32] Priority Oct. 21, 1967 [33] Germany [54] NARCOSIS APPARATUS 7 Claims, 1 Drawing Fig.

[52] US. Cl 261/39,

[51] int. Cl 'A61m 17/00 [50] Field of Search 128/188;

[56] References Cited UNlTED STATES PATENTS 2,553,446 5/1951 Edmondson et a1. 128/188 3,107,689 10/1963 Schreiber et a1 128/188(X) 3,219,325 11/1965 Brown 261/39(X) 3,420,232 1/1969 Bickford 128/188 max. V01

FOREIGN PATENTS 648,191 1/1951 Great Britain Primary Examiner-Tim R. Miles ArtorneyCurtis, Morris & Safford ABSTRACT: An apparatus for the vaporization of an anesthetic has been provided which apparatus achieves improved control in respect to the amount of anesthetic administered to a patient. The apparatus comprises a distribution chamber for a gas, a first conduit from the distribution chamber into a chamber in which the anesthetic is vaporized, a temperature sensing means in said vaporization chamber, a second bypass conduit from the distribution chamber having a throttle means interposed therein, said second conduit leading to a mixing chamber, an outlet conduit leading from the NARCOSIS APPARATUS This invention relates to an apparatus for an anesthetic, more particularly, a vaporizer apparatus for an anesthetic provided with a bypass connected in parallel to the vaporizer.

A vaporizer apparatus for anesthetic having a bypass connected in parallel to the vaporizer in which control valves are provided in the bypass and the vaporizer lines is already known. For this apparatus, there can be provided both in the bypass branch line and in the vaporizer branch line an adjustable choke in which the ratio of the gap width of the choke to the length of the choke in every possible position of the valve is less than By this apparatus, it is achieved that upon a variation of the admission pressure, and thus of the rate of flow, no change in the mixture ratio will result.

Furthermore, there has been proposed an apparatus of the above-described type in which the two chokes are directly coupled with each other in such a manner that when one is adjusted in the open" direction, the other is moved in the close" direction. In this manner, there is obtained a simple control of the apparatus.

In the known vaporizers for anesthetics which anesthetics are liquid at normal temperature, a disadvantage of relatively great dependence upon temperature is present. When the temperature of the apparatus increases, the vapor pressure of the anesthetic rises relatively rapidly; but the degree of saturation of the stream conducted over the anesthetic is established in accordance with the value of the vapor pressure. As the vapor pressure is relatively strongly dependent upon temperature, there is the danger that even with only a relatively minor change in temperature of a few degrees, there may possibly be produced a drastic change measured in percent by volume.

In order to avoid these disadvantages, it is already known to measure the temperature of the vaporizer for anesthetic by a thermometer, the anesthesiologist being given present in the lines being given a table on basis of which which he variably adjusts the valve present in the lines, depending on thetemperature read. This presupposes a continuous, careful observation of the thermometer, and it requires constant readjustment. Furthermore, the calibration there is obtained a socalled family of curves for different temperatures and concentrations of an anesthetic. Furthermore, the anesthesiologist must not only be able to follow the temperature, but also to read the calibration curve.

Vaporizers for anesthetics which are equipped with a socalled automatic temperature equalizer are also known. It consists of an orifice arranged in the stream of gas. The orifice is covered to a greater or lesser extent by a thermal bimetallic strip, depending on the prevailing temperature. In this manner, variations in temperature are to be counteracted by variations in the resistance to flow. When using thermal bimetallic strips, the danger of aging is present. Furthermore, it is possible that the adjustment is entirely distorted by an accidental bending of the bimetallic strip.

Similar disadvantages are present when operating a vaporizer for liquid anesthetics having low vapor pressure at normal temperature, i.e., so low that the saturation concentration is required for clinical operation. In the case of such apparatus, the gas stream conducted through the bypass must be particularly strongly throttled or shut off so that the anesthesiologist very likely must work with the saturation concentration. The operating of this apparatus has the same disadvantages as described above. lnasmuch as the temperature controlled regulating member is arranged in the vaporizer branch line in these apparatus, the bypass lines in these apparatus do not automatically adjust or adapt to the formation of a gas mixture with saturation concentration.

Hence, the object of the present invention is to avoid the disadvantages of the known apparatus and to provide an apparatus for anesthetics which on the one hand adjusts the concentration of the gas leaving the vaporizer so that it is practically constant even in case of variations in temperature and that furthermore, particularly when using anesthetics in the case of which the bypass line is entirely closed upon the reductions in temperature beyond a given amount, the concentration of the anesthetic gas leaving the apparatus has at least the saturation concentration at the given temperature.

Thus, the invention relates to a vaporizer for anesthetic having a bypass line which contains an adjustable choke or throttle and is connected in parallel with the vaporizer. The invention resides in the fact that the stem of the bypass choke or throttle valve is provided with a stem extension which extends beyond the valve seat, passes through the wall of the vaporizer chamber in gastight manner and protrudes into said chamber. Further, a sleeve bearing the movable valve part and surrounding the stem extension of the stem is provided on the end of said extension. The coefficient of thermal expansion of the material from which the stem extension is made is smaller than the coefficient of thermal expansion of the material of which the sleeve connected to the movable valve is made.

The present invention has the advantage that upon a cooling of the anesthetic such as can occur in particular from the cold produced by vaporization, and the resultant decrease in the concentration of the anesthetic in the stream of gas leaving the vaporizer chamber, the quantity of gas passing through the bypass line is also reduced. Furthermore, the quantity of gas flowing through the vaporizer chamber can be thereby increased. An increase in the quantity of gas flowing through the vaporizer chamber causes increases vaporization so that to this extent the reduction of the vaporization of the anesthetic which results from the decrease in temperature as a result of the reduction of the vapor pressure is as a whole again counteracted. Moreover, the apparatus can be so adjusted that with a drop in the temperature below a given value, the bypass line is closed in the novel apparatus so that the entire quantity of gas flowing through the apparatus must pass through the vaporizer chamber. The concentration of the anesthetic in the gas leaving the apparatus is then equal to the saturation pressure of the anesthetic at the temperature selected.

Further details of the invention are illustrated below or defined in the appended claims or with reference to the embodiment shown schematicallyby way of example in the accompanying drawing.

The initial gas used as a carrier for the anesthetic can consist for example of oxygen, oxygen and nitrous oxide, or the like. It passes through the pipe 1 into the distributing chamber 2. The latter is connected via the conduit 5 with the vaporizer chamber chamber 9, the outlet line 8 of which vaporizer chamber is connected with the mixing chamber 7. The choke or throttle 3 is interposed in said line. From the distributing chamber 2 the bypass line 6 leads via the other choke or valve 4 also to the mixing chamber 7. Both chokes or throttles 3 and 4 are adjustable and are characterized by the fact that the ratio of slot width 11 to slot length 10 is less than 10 in every position used. The chokes or throttles. are of the double-cone valve type.

The two chokes 3 and 4 have stems 14 and 15, respectively, which are rigidly connected with the gear wheels 16 and 17, respectively, which in their turn mesh with each other so that whenthe handwheel 18 is turned for instance in clockwise direction while the stem 14- turns in counterclockwise direction while the stem 14 turns in counterclockwise direction. The two spindles in the embodiment shown by way of way of example have their threads 19 in the same direction so that upon the movement described the one choke 4 is finally closed and the other choke 3 is fully opened.

lnstead of the connection by means of gear wheels the chokes 3 and 4 can also be connected together by some mechanical means for example by levers, in such a way that upon the opening of the one choke, the other is closed to the same degree or to a different degree. In the case of the embodiment shown by way of example, the chokes 3 and 4 are so designed and adjusted that at a concentration setting of zero the choke 3 present in the path through the vaporizer chamber 9 is closed, while the choke 4 is fully opened. On the other hand, in the same illustration, at the maximum concentration setting, the choke 4 present in the bypass 6 is closed, while the choke 3 is fully opened.

The choke 4 is designed as follows. The stem is provided with a stem extension 21 which extends beyond the valve seat 4a, passes in gastight fashion through the wall of the vaporizer chamber 9 and extends into said chamber. At the end 22 of this stem extension, there is fastened a sleeve 23 which surrounds the extension 21 and bears the movable valve part 4b. For this purpose, the end 22 of the stem extension 21 bears a transverse pin which engages in two bores at the end of the sleeve 23.

The materials of which the extension 21 and the sleeve 23 are formed are so selected that the coefficient of thermal expansion of the material of the extension 21 is less than the coefficient of thermal expansion of the material of which the sleeve 23 made. Thus, the stem extension 21 can, for instance, consist of Ni 36 (lnvar alloys), Le, a material of very low thermal expansion, or of a suitable stainless steel, whereas the material in the sleeve is made of Teflon, nickel, indium nylon, or a material having a thermal coefficient or expansion larger than lnvar alloys or a suitable stainless steel. These materials must be inert to the anesthetics employed.

Upon the passage of the stream of gas through the vaporizer chamber 9, the anesthetic vaporizes and cools down. This results in a lowering of the vapor pressure whereby, with constant gap widths of the chokes 3 and 4, the concentration would decrease. In the apparatus of the invention, however, the sleeve 23 shortens more than the extension 21 contracts as a result of the cooling. In this way, the gap of the choke 4 is made smaller and, thus, the resistance of this choke is increased. Accordingly, less gas flows through the bypass line while on the other hand more gas passes through the vaporizer' chamber 9 so that the total quantity of anesthetic vaporized remains the same and thus, the concentration given off is held constant.

The choke 4 can now be so adjusted that it closes at a predetermined temperature. The total quantity of gas then flows through the vaporizer chamber 9. The anesthetic gas as the saturation concentration of the anesthetic. When the temperature drops further, there is established in the gas mixture leaving the apparatus in an event the concentration of anesthetic which corresponds to the corresponding saturation concentration. An increase in the concentration of the anesthetic is no longer possible in this case. In order to indicate to the anesthesiologis what concentration is present when the choke 4 is'closed, there is provided a temperature measuring device 24 whose sensor or feeler 26 lies in the liquid anesthetic. The temperature measuring device 24 can now be calibrated directly in saturation concentration so that the anesthesiologist can read off from this apparatus not only the temperature but at the same time the saturation concentration obtainable at the temperature prevailing at the time.

lclaim:

1. An apparatus for vaporizing an anesthetic having a bypass line in parallel to the vaporizer chamber comprising: a throttle on said bypass line, said throttle having a valve seat, a valve stem, a movable valve element, a valve stem extension protruding into said vaporization chamber, a sleeve surrounding the valve stem extension, said sleeve and stem extension being in a gastight relationship to said vaporization chamber, said valve stem extension being of a material having a thermal coefficient of expansion less than the thermal coefficientof expansion of said sleeve.

2. The apparatus for vaporizing an anesthetic according to claim 1, wherein the valve stem extension is in the vaporization chamber below a normal liquid level of an anesthetic being vaporized 3. The apparatus according to claim 1, wherein the stem extension and the sleeve are fastened by a terminal coupling means.

4. An apparatus for the vaporization of an anesthetic providing improved control in respect to the amount of anesthetic administered to a patient comprising: a distribution camber for a gas, a first conduit from the distribution camber into a chamber in which the anesthetic is vaporized, a temperature sensing means in said vaporization chamber, a

second bypass conduit from the distribution chamber being a throttle means interposed therein, said second conduit leading to a mixing chamber, an outlet conduit leading from the vaporization chamber to the mixing chamber and having a valve means interposed therein, said throttle means in said bypass conduit having an annular slot defined by a movable element on a throttle stem extension, said stem extension protruding into the vaporization chamber and having a sleeve surrounding the same, means for fastening said sleeve and said stem extension, said sleeve being of a material having a higher thermal coefficient of expansion than the material of which the stern extension is made, and said throttle and valve means having means provided to engage each other.

5. The apparatus according to claim 4, wherein the throttle and valve means are coupled to each other dependently moving the other in the opposite direction from closing to opening.

6. The apparatus according to claim 5, wherein the throttle and valve means have stem threads running in the same direction and wherein the stems of said throttle and valve means bear gear wheels which are meshing with each other.

7. The apparatus according to claim 1, wherein the temperature sensing means is coupled to a scale calibrated to a vapor saturation indicating scale. 

